Investigating officer Detective Sergeant Adam Billingham Milton Keynes CID, said: “I am appealing for anyone who was in the area at the time of the incident or anyone that saw anything unusual to contact police.”

She added: “ It is believed that two other cars stopped to try and help, however so far the occupants are yet to come forward.

“It may be that this was an innocent incident however we need to check on the welfare of the person involved so if anyone was either involved themselves with this incident or saw it happen please contact us so we can establish the circumstances.”

The man is described as white, of large build with brown hair. The woman is described as white, aged in her late twenties and was wearing a white jumper.